The present invention relates generally to the art of molding tires. More particularly, the present invention relates to blades which are inserted in slots in tire molds for forming sipes, i.e., short narrow grooves in the tread of a tire. Illustrations of various forms of blades are found in U.S. Pat. No. 6,264,453, the disclosure of which is hereby incorporated herein by reference.
Recently, the tire industry has begun to convert from an aluminum cast process for molding tires to the use of engraved steel or aluminum molds. Engraving is considered desirable to provide a more accurate tire, and state of the art 5-axis machines make engraving economical.
Short thin slots are engraved into the tire mold for insertion of blades, which have an elongate edge portion or base received in the slot and a body or operative portion which extends from the slot to form the sipe during the molding of the tire tread. The slot depth may typically be about 0.190 inch.
Blades are typically about xc2xc to 2 inches long and made from a running length or strip of metallic material such as steel, stainless steel, or inkanel. The strip is generally about 0.02 to 0.04 inch thick and has a width of about xc2xd to 1xc2xd inches (which define the thickness and height respectively of the blade). The strip may be in solid form or perforated.
An epoxy has been used to hold the blades within the slots, to withstand a force in the range of several hundred pounds.
However, the blades tend to fail and come loose after a short time (perhaps 2 years). Moreover, it is difficult and time consuming to use the epoxy to install the blades.
A conventional slot for a tire mold blade has a depth across its entire length of about 0.190 inch, requiring a substantial amount of machining.
It is accordingly an object of the present invention to provide a means for attaching a blade so that it can withstand the forces typically encountered by blades for a long period of time.
It is another object of the present invention to easily and quickly insert the blades.
It is a further object of the present invention to reduce the amount of tire mold machining for blade insertion and therefor reduce the machining cost.
In order to easily and quickly attach a blade to a tire mold so that it lasts a long time, in accordance with the present invention, the blade is formed to have at least one self-locking portion which is receivable within a slot or slit in the mold wherein, as the blade is tapped with the self-locking portion partially in the slot or slit, a wedge member forces at least one tab portion into a locking relation in the slot or slit as the self-locking portion is driven fully into the slot or slit.
The above and other objects, features, and advantages of the present invention will be apparent in the following detailed description of the preferred embodiment of the invention when read in conjunction with the accompanying drawings wherein the same reference numerals depict the same or similar parts throughout the several views.